1. Field of the Invention
The present invention relates to user interfaces in general and more specifically to a user interface for an ultrasound imaging device and to a handheld ultrasound imaging device.
2. Description of Prior Art
Ultrasonic imaging is a frequently used method of analysis for examining a wide range of materials. Ultrasonic imaging is especially common in medicine because of its relatively non-invasive nature, low cost and fast response times. Typically, ultrasonic imaging is accomplished by generating and directing ultrasonic sound waves (an ultrasonic beam or signal) into a medium under investigation using a set of ultrasound generating transducers and then observing reflections generated at the boundaries of dissimilar materials, such as tissues within a patient, also using a set of ultrasound receiving transducers. A single transducer, however, may be used rather than an array of transducers. The receiving and generating transducers may be arranged in arrays and the same transducer may be used for both receiving and generating ultrasonic signals. The reflections are converted to electrical signals by the receiving transducers and then processed, using techniques known in the art, to determine the locations of echo sources. The resulting data is displayed using a display device, such as a monitor.
Typically, the ultrasonic signal transmitted into the medium under investigation is generated by applying continuous or pulsed electronic signals to an ultrasound generating transducer. The transmitted ultrasonic signal is most commonly in the range of 40 kHz to 30 MHz. The ultrasonic signal propagates through the medium under investigation and reflects off interfaces, such as boundaries, between adjacent tissue layers. Scattering of the ultrasonic signal is the deflection of the ultrasonic signal in random directions. Attenuation of the ultrasonic signal occurs when some of the ultrasonic signal is lost while the signal travels. Reflection of the ultrasonic signal is the bouncing off of the ultrasonic signal from an object and changing its direction of travel. Transmission of the ultrasonic signal is the passing of the ultrasonic signal through a medium. As it travels, the ultrasonic signal is scattered, attenuated, reflected, and/or transmitted. The portions of the reflected ultrasonic signals that return to the transducers are detected as echoes. The detecting transducers convert the echo signals into electronic signals and, after amplification and digitization, furnish these ultrasonic signals to a beam former. The beam former calculates locations of echo sources and typically includes simple filters and signal averagers. After beam forming, the calculated positional information is used to generate two-dimensional data that can be presented as an image.
As an ultrasonic signal propagates through a medium under investigation, additional harmonic frequency components are generated. These components are analyzed and associated with the visualization of boundaries or image contrast agents designed to re-radiate ultrasonic signals at specific harmonic frequencies. Unwanted reflections within the ultrasound device can cause noise and the appearance of artifacts (i.e., image features that result from the imaging system and not from the medium under investigation) in the image. Artifacts may obscure the underlying image of the medium under investigation.
The ultrasonic signal intensity as a function of position may oscillate rather than fall off monotonically as a function of distance from the center of the beam that forms the ultrasonic signal. These oscillations in ultrasonic signal intensity are often called “side lobes.” In the prior art, the term “apodisation” refers to the process of affecting the distribution of ultrasonic signal intensity to reduce side lobes. In the remainder of this specification, however, the term “apodisation” is used to refer to tailoring the distribution of ultrasonic signal intensity for a desired beam characteristic such as having a Guassian or sinc function (without the side lobes) distribution of ultrasonic signal intensity.
Steering refers to changing the direction of an ultrasonic signal. Aperture refers to the size of the transducer or group of transducers being used to transmit or receive an ultrasonic signal.
The prior art process of producing, receiving and analyzing an ultrasonic signal (or beam) is called beam forming. The production of ultrasonic signals optionally includes apodisation, steering, focusing and aperture control. Using a prior art data analysis technique, each ultrasonic signal is used to generate a one-dimensional set of echolocation data. In a typical implementation, a plurality of ultrasonic beams is used to scan a multi-dimensional volume. Imaging, in general, and ultrasound imaging, in particular, are utilized in many medical procedures in order to detect a patient's condition. For example, ultrasonic imaging is commonly used to detect and monitor the growth and health of fetuses or to detect and assist in the diagnosis of liver and kidney pathology.
Many medical ultrasound imaging systems have been designed, manufactured and successfully used, each varying in presentation, complexity, and ergonomics. In some cases, the user interfaces are cumbersome to operate. Even more cumbersome are those user interfaces requiring two hands to operate or transport resulting in encumbrance of using the system for real-time examinations. Other examples of difficulties that arise in the case of a handheld device are navigation and selection of the user interface items using one hand or one thumb. It may be desirable, in handheld ultrasound devices, the user interface allow for quick and efficient interaction supported by intelligent user interface behavior, context sensitivity, data dependent optimization and the ability to self-adapt to user behavior.
Further, as medical services tend to be expensive, the easier a medical professional can operate the user interface, the more patients the medical professional can serve and the less the medical professional will need to charge for their services.